Method of rendering cellulosic material non-adherent and article produced thereby



United States Patent IVIETHOD OF RENDERING CELLULOSIC MATE- RIALNON-ADHERENT AND ARTICLE PRO- DUCED THEREBY Herbert J. Leavitt,Schenectady, N.Y., assignor to General Electric Company, a corporationof New York No Drawing. Filed Mar. 26, 1958, Ser. No. 723,965

7 Claims. (Cl. 117-143 This invention is concerned with renderingcellulosic materials non-adherent to various organic solids. Moreparticularly, the invention is concerned with a process for renderingpaper or paperboard non-adherent to normally adherent materials such as,for instance, asphalts, bitumen, tars, waxes, paraffin solids,flour-containing pastes and frozen foodstuffs, and other high molecularweight polymers which process comprises treating the said cellulosicmaterial with a mixture of ingredients comprising (1) a linearpolydimethylsiloxane containing a terminal silicon-bonded hydroxy group,(2) a polyalkyl silicate, and (3) a metallic salt selected from theclass consisting of dibutyl tin dilaurate and dibutyl tin diacetate.

Cellulosic fibers in the form of cel'lulosic papers and paperboard areused extensively as confining and shipping means for various highlyadhesive materials including such organic compositions as asphalt orpitch, tar, various unvulcanized rubbers, particularly syntheticrubbers, other high molecular weight organic polymers used as adhesives,etc. For optimum use of these cellulosic containers, it is essentialthat they be capable of being readily separated or stripped from thecargo contained therein. Thus, in the transportation and shipment ofasphalt used for roofing purposes, the asphalt is generally poured whilestill hot into a container, such as a carton, bag or drum whose sidesare cellulosic in nature. After cooling, the asphalt becomes quite hardand can be readily transported with little difficulty. At itsdestination of use, it is essential that this paper in Whatever form becapable of being readily stripped from the asphalt so as to permit easyaccess to the latter without any extraneous portions of the paper orfibers thereof adhering to the asphalt so as to undesirably affect theconstitution of the asphalt.

Various treatments have been accorded these types of papers which areoften referred to as anti-blocking paper or release paper). One methodfor treating the paper to render it anti-blocking comprises treating thepaper in a three-coat operation with (1) finely divided clay and casein,(2) finely divided clay, and (3) polyvinyl acetate. Such paper providesrelease by fracture of the clay coating, but the polyvinyl acetateremains on the adhesive material. Another method commonly employed inthe art involves applying several thicknesses of polyethylene to thepaper, usually by treating the latter with solutions of thepolyethylene. A still further method for treating cellulosic material torender it non-adherent, particularly to asphalt and to permit it to bereadily removed from direct contact with the latter, involves depositinga double coating of cellulosic materials, the first coating being ofclayand the second coating being of methyl cellulose and starch.

ice

However, all the foregoing methods have been exceedingly expensive andin many respects have not been too satisfactory since too often it hasbeen found that these adhesive materials, particularly asphalt, whichapparently has a high affinity for cellulosic fibers, stick to theanti-blocking paper so that great difficulty is encountered inattempting to separate the latter from the asphalt.

U.S. Patent 2,588,367 describes the use of methyl hydrogen polysiloxanesin combination with water-soluble cellulose ethers for the purpose oftreating anti-blocking paper to render it less adherent to ordinarilyadhesive organic compositions. Although such combinations of ingredientsare ordinarily helpful in reducing the adhesive properties of the paper,nevertheless much is left to be desired from such treatment of thepaper. Often, the release properties are unreliable and the releasecharacteristics are not uniform throughout the surface of the paper. Inaddition, it is essential that, in order to obtain optimum releaseproperties, the treated paper be aged for extended periods of time,e.g., by storage before it is useful for release purposes; this isnecessary because accelerated aging by high-temperature treatment is notusually available commercially in paper-treating establishments.Furthermore, paper such as parchment paper cannot be heated above 1125"C. without deleteriously affecting the paper. Moreover, after treatmentof paper with the methyl hydrogen polysiloxane, the abhesivecharacteristics (i.e., the release properties) tend to decrease withtime so that after long term storage, such treated paper no longer showsabhesive characteristics.

In addition to the difficulties described above, particularly when usingmethylpolysiloxanes for anti-adhesion (abhesive) purposes, and even whenusing the more currently employed methyl hydrogen polysiloxanes for thispurpose, it has been found that although release properties areimproved, nevertheless, there is an undesirable tendency of the siliconein the abhesive paper to migrate to the surface of the paper therebycoming in contact with the material which it is desired to release.Often the abhesive paper is in contact with compositions which aredestined to be used for adhesion applications, and the tack or theadhesion is undesirably reduced as a result of this migration of theorganopolysiloxane from the treated release paper to the adhesive.

Unexpectedly, I have discovered that a certain mixture of ingredientscan be used to treat release paper whereby the various difficultiesrecited above are obviated. In addition, release paper treated withthese compositions shows no evidence of migration of theorganopolysiloxane therein to the surface so as to con taminate anymaterial with which the release paper may come in contact. Thecompositions which I have found to be so eminently suitable in thepractice of the present invention comprise (l) a linearpolydimethylsiloxane having a terminal silicon-bonded hydroxyl group,(2) a polyalkyl silicate, e. g., polyethyl silicate, etc., and (3) a tinsalt, selected from the class of dibutyl tin dilaurate and dibutyl tindiacetate.

The polydimethylsiloxanes employed in the practice of the presentinvention are those having the general formula zls'iiol where n is aninteger greater than 1, for instance, from 25 to 100,000, and Z is aradical selected from the class consisting of the --OH and CH radicals.These polydimethyl-siloxanes containing the terminal silicon-bondedhydroxyl group or groups (hereinafter referred to aspolydimethylsiloxane), are soluble in organic solvents such as xylene,toluene, trichloroethylene, etc., and are preferably of a fluidnature-which may range in viscosity from highly fluid materials todifficultly flowable compositions; the viscosities of suchpolydimethylsiloxanes may range from about 50 to 2,000,000 centipoiseswhen measured at 25 C. The presence of up to 0.5 mol percent oftrimethylsiloxy units [(CH SiO in the linearmethylpolysiloxane willfurnish the terminal CH group so as to have a chain-stopping (CH SiOgroup, in addition to an -OH group, in the linear polydimethylsiloxane.

These polydimethylsiloxanes may be prepared by any one of severalwell-known methods. Thus, the high viscosity polydimethylsiloxanes maybe obtained by condensing the hydrolysis product ofdimethyldichlorosilane with either acidic or alkaline catalysts such ashydrochloric acid, sulfuric acid, potassium hydroxide, etc.Alternatively, one can heat cyclic polymers of the formula where m is aninteger equal to from 3 to 6, for instance,octamethylcyclotetrasiloxane, with an alkaline catalyst such aspotassium hydroxide, cesium hydroxide, etc. (in an amount equal, byweight, to from about 0.001 to 0.1% based on the weight of theoctamethylcyclotetrasiloxane) at temperatures of from 125 to 175 C. fortimes ranging from about 15 minutes to 2 hours or more and thereafter,if desired, removing the alkaline catalyst to yield apolydimethylsiloxane of Formula I having a viscosity of from about700,000 to 2,000,000 centipoises when measured at 25 C. By incorporatingduring this polymerization, small amounts of sources of the CHchain-stopping radical, e.g., from 0.01 to 0.1%, by weight, based on theweight of the octamethylcyclotetrasiloxane, of hexamethyldisiloxane,decamethylpolysiloxane, etc., one can obtain linear olydimethylsiloxaneshaving one terminal hydroxyl group and one terminal CH group (seeFormula I). Also present will be polydimethylsiloxanes containing twoterminal hydroxyl groups randomly distributed with the monohydroxysubstituted polydimethylsiloxane.

When lower viscosity polydimethylsiloxanes containing terminalsilicon-bonded hydroxyl groups are desired, one can treat the highmolecular weight products ob tained above with water to reduce theviscosity of the polymer to within the range from about 50 to 100,000centipoises at 25 C. This can be accomplished by blowing steam acrossthe surface of the high molecular weight product or through the polymerfor 'a sufficient time to give the lower viscosity material having thedesired silanol content. Such compositions and various methods forpreparing the same are more particularly described in U.S. Patent2,607,792. The use of steam in this fashion will cause a decrease in theviscosity of the polymer while at the same time the formed linearpolysiloxane will have terminal silicon-bonded hydroxy groups. 7

An alternative method for making the linear organopolysiloxanecontaining terminal silicon-bonded hydroxy groups comprises adding waterto the high molecu lar weight polymer described above in such amountthat when heated at elevated temperatures, for instance, 150 to 170 C.,the viscosity is reduced to the desired level of 1,000 to 50,000centipoises. The amount of water used will vary depending upon suchfactors as the molecular weight of the polymer being treated, the timeand temperature at which the mixture of high molecular weightorganopolysiloxane and water will be heated, the ultimate viscositydesired, etc.

The amount of water used to reduce the molecular weight can be readilydetermined. For instance, one can obtain a linear fluidmethylpolysiloxane containing terminal silicon-bonded hydroxy groups andhaving a viscosity of from 1,000 to 2,000 centipoises at 25 C. byheating a high molecular weight methylpolysiloxane (prepared inaccordance with the directions above) of about 2,000,000 centipoiseviscosity, with only 0.5 percent, by weight, thereof water for about 2hours at 150 to 170 C.

The polyalkyl silicate employed in the practice of the present inventioncan be obtained by efiecting partial hydrolysis in water of monomericorganosilicates having the forinula (RO) Si where R is a lower alkylradical containing from 1 to 5 carbon atoms, for instance, methyl,ethyl, propyl, butyl, amyl, etc., radicals. Such hydrolysis products aregenerally obtained by effecting partial hydrolysis in water of theparticular monomeric organosilicate in the presence of small amounts ofacid to a point where it is still water-insoluble and it is stillpossible to isolate a liquid, partially hydrolyzed organosiliconcompound. Thus, taking as a specific example the controlled partialhydrolysis of ethyl silicate having the formula (C H O) Si, thehydrolysis of the latter may be carried out by adding acids oracid-forming metal salts to the liquid monomeric organosilicate, forinstance, FeCl CuCl AlCl SnCl.,, etc., and thereafter efiecting suitablehydrolysis of this mixture of ingredients in water to obtain thetwo-phase composition from which the water-insoluble, partiallyhydrolyzed organosilicate can readily be separated from the aqueousphase and catalyst.

I have unexpectedly found that contrary to what might be expected,dibutyl tin dilaurate and dibutyl tin diacetate gave minimum migrationof the methylpolysiloxane and were able to be used in lowerconcentrations than when one employed metallic soaps even tin soaps,such as tin octoate, tin naphthenate, tin oleate, and even such ametallic salt as butyl tin trioctoate, which is closely akin to dibutyltin dilaurate and dibutyl tin diacetate.

The above essential ingredients used for treating cellulosic materialsto render them abhesive in the form of a coating material which isnon-migratory as far as the methylpolysiloxane contained therein isconcerned, are advantageously dissolved in a solvent such as, forinstance, xylene, toluene, mineral spirits, trichloroethylene,perchloroethylene, etc. The above-described mixture of essentialingredients composed of the polydimethylsiloxane, the polyalkylsilicate, and the specific dibutyl tin salt in combination with asolvent can be used as treating baths for cellulosic materials such ascellulosic sheet material, parchment paper, kraft paper, linen ragpaper, rice paper, glassine, cellophane, sulfite cellulose paper and thelike; as well as sheeting or boxing materials such as paperboard,cardboard, pulpboard,

and pasteboard.

A formulation comprising a solution of the above inbasis as specifiedabove, an alternative means for calculating the proportion of thedibutyl tin salt comprises basing it on the amount of tin containedtherein; on such a basis one advantageously employs at least 0.1%,preferably from 0.5 t 2 by weight, tin either in the form of dibutyl tindilaurate or dibutyl tin diacetate, based on the weight of thepolydimethylsiloxane. The amount of dibutyl tin salt employed willdepend upon such factors as, for instance, the particular metal saltused, its efiect on the stability of emulsions, where emulsions areused; the type of organopolysiloxane employed, the type of paper towhich the treating composition will be applied,

the solubility of the tin salt, as well as the medium in which the tinsalt will be used, the treating conditions including temperature andtime of treatment, etc.

Following treatment of the cellulosic material with the solution of theabove described ingredients, the cellulosic material is advantageouslydried by passing the treated paper over heated rolls (or cans)maintained at temperatures of about 50 to 90 C., for from 2 to 20minutes or more. The use of circulating hot air at temperatures of from50 to 125 C. may also be used for times of from 15 seconds to 3 minutesto effect curing of the treated paper. 7 This drying step .will bringout the optimum re.- lease properties of the paper Without further heattreatment, and such optimum release properties are immediately availablewithout requiring aging or storage of the treated paper.

In order that those skilled in the art may better understand how thepresent invention may be practiced, the following examples are given byway of illustration and not by way of limitation. All parts are byweight.

The polyethyl silicate employed in the following examples is sold byCarbide and Carbon Chemicals Corporation of New York, N.Y., under thename of Ethyl Silicate 40 and is a mixture of ethyl polysilicates havingabout 40 percent available silica and is derived from the controlledhydrolysis of tetraethyl silicate, the formula for said polyethylsilicate being described as follows:

where Et represents the C H group. [Additional information for makingthe partial hydrolysis products of the monomeric organosilicon compoundsdescribed above maybe foundin the article by H. D. Hogan and C. A.Setterstrom entitled EthyLSilicates, in Industrial and EngineeringChemistry, volume 39, page 1364, No. 11 (1947).]

The high viscosity polydimethylsiloxane containing a terminalsilicon-bonded hydroxyl group (hereinafter referred to asmethylpolysiloxane No. 1) used in the following examples had a viscosityof around 3,000,000

centipoises when measured at 25 C. and had a ratio of approximately twomethyl groups per silicon atom. This high viscosity composition wasobtained by heating octamethylcyclotetrasiloxane with about 0.001%; byweight thereof, potassium hydroxide and with about 0.05%, by weight,thereof, decamethylpolysilox ane for about 2 to 4 hours at about C.until a benzenesoluble product was obtained.

The low molecular weight polydimethylsiloxane containing two terminalsilicon-bonded hydroxyl groups (hereinafter referred to asmethylpolysiloxaneNo. 2). employed in the following examples wasobtained by mixing with the high molecular weight polydimethylsiloxaneabout 0.5% weight thereof water, and the mixture of ingredients heatedwith stirring for about 2 hours at to C. until a product having aviscosity of about 3,700 centipoises (when measured at about 25 C.) wasobtained.

In the following tests, therelease characteristics of the treated paper(parchment paper was used) were determined by pressing "'(byhand) astrip of surgical adhesive tapeon the surface of the treated paper andlifting'the tape from the paper; evaluation of the release wasdetermined by assigning numerical values as follows:

0-No lifting of paper whatever 1--One edge of paper lifted up to A 2-Oneedge of paper lifted A" to 1" 3One edge of paper lifted l to 2" 4-Paperfalls off after being lifted by tape 5Paper shakes off after beinglifted by tape 6Paper will not shake off Migration of the silicone fromthe treated paper to the surface with which. it came in contact wasdetermined by observing the detackification of a surgical adhesive tape(loss of tack of the adhesive) caused by migration of the silicone fromthe surface of the paper to the adhesive on the tape. This wasaccomplished by pressing (by hand) a strip of adhesive tape onto thesurface of the treated paper five times in five different areas. Thistechnique greatly accelerated determination of migration because theadhesive would be expected to pull off silicone which, if givensuflicient time, might migrate of its own accord to the material withwhich it came in contact. Surgical adhesive tape was used because amajor application of release paper is its use as interleaving sheetswhere the treated paper is in intimate contact with adhesives and noloss of tack can be tolerated in such an application. A strip of theadhesive tape was then lifted from the paper and folded over so that theadhesive surface (which had been in contact with the release paper) wasbrought into contact with itself. The pull required to separate theadhesive surface from itself (evaluated subjectively as to poor, fair,fair-good, and good tack) compared with tape which had not been incontact with release paper was used as a measure of detackification ofthe tape and thus as a measure of migration of the silicone material.The methylpolysiloxane pickup was within the range from about A to 1%%,by weight, based on the weight of the parchment paper used.

EXAMPLE 1 In this example a solution was prepared composed ofmethylpolysiloxane No. 1, ethyl silicate 40, and toluene. The percenttoluene in the solutionwas held substantially constant so that itrepresented about 70 percent of the total weight of the aforesaid threeingredients, while the ethyl silicate 40 and the methylpolysiloxane No.l were varied. Catalyst solutions were also prepared from variousmetallo-organic salts in which the metallic salt in the catalystsolution comprised, by weight, about 33 percent, and the solvent(toluene) used to make the solution comprised about 67 percent, byweight. Various treating solutions were prepared by mixing together themethylpolysilox anepolyethyl silicate solution with the catalystsolution. The bath life of the mixture of the catalysts and themethylpolysiloxane solutions was determined by noting the time withinwhich gelling of the active ingredients in the treating solutionoccurred.

Parchment paper was treatedwith the various treating baths by immersingthe paper. in the bath, removing the treated paper and'pa'ssing itbetween squeeze rolls, and heating the treated paperat a temperature ofabout 65 C. for about 3 minutes. This method for treatment of parchmentpaper was followed in all the following examples as well. The followingTable I shows the percent methylpolysiloxanelNo. .1, and the percentpolyethyl silicate 40 in each of the treating baths, as well as theparticular metallo-organic salt used and theperce'nt of such saltexpressed as percent metal. All percents are on a weight basis based onthe total weight of the active r ingredients and the toluene solvent,the toluene comprising the difference between the weight of the activeingredients and 100 percent. In the following tests, the bath: life ofthe treating solutions ranged from 2 to 15 hours with the exception ofTest No. 14 where the treatingzba-th'gelled after .15 hours.- 1 i Table1 Percent Percent Percent Methyl- Ethyl Catalyst 4 Test po1y-S11-Silicate Catalyst (Expressed Release Tack N0. oxane 40 as the No. 1Metal) '4 0.12 Dlbutyl tin dllaurate 0.08 Good. 4 0.12 Dibutyl tindiacetate 0. 08 0 Do.

10 1.0 Dibutyl tin dilaurate... 4. 4 0 Do.

10 1. 0 Dibutyl tin diacetat 4. 4 0 Do. 4 0.12 Lead tetra octoate...0.08 0 Fair. 4 0.12 0. 08 0 Do. 4 0.12 0.08 0 Do. 4 0. 12 0. 08 0 Do. 40.12 0.08 0 D0. 4 0.12 0.08 0 D0.

10 1.0 Tin naphthenate 4. 4 0 Do.

10 1. 0 Tin octoate 4. 4 0 Do.

10 1.0 Tin oleate 4. 4 0 Do.

It will be noted from the above Table I that although variousorgano-metallic salts can be used to catalyze the mixture of thepolydimethylsilox-ane and the polyethyl silicate, for retention ofmaximum tack, that is, minimum migration of the methylpolysiloxane,dibutyl tin dilaurate and dibutyl tin diacetate showed betterperformances at both low and high concentrations of catalyst,methylpolysiloxane, and polyethyl silicate concentrations'.

EXAMPLE 2 This example illustrates the importance of including thepolyalkyl silicate with the methylpolysiloxane and the organo-metalliccatalyst in order to obtain a treated paper which shows good releasewithout migration as shown by full retention of tack by the adhesivetape. More particularly, toluene solutions were prepared ofmethylpolysiloxane No.1, ethyl silicate 40 and various organometallicsalts including the dibutyl tin dilaurate and dibutyl tin diacetatefound to give the improved performance more particularly recited above.The method for preparing the catalyzed solutions was the same as thatused to prepare the solutions described in Example 1. The followingTable II shows the proportions and ingredients used as well as the testresults on the treated paper. In all instances the bath life wassatisfactory for 8 hours. The paper used was again parchment paper andwas tested in the same manner as recited in Example l.

the ethyl silicate 40, and within the range of at least 0.16 to 4.4percent for the dibutyl tin dilaurate (which was the only catalyst usedin this example), each based on the total weight of the treating bath,good results were obtained regardless of the proportions used.

1 Bath life in each instance was satisfactory for at least 2 hours.

EXAMPLE 4 This example illustrates that in addition to toluene, one canalso employ other diluents or solvents for the treating bath. Moreparticularly, various solvents, such Table II Percent Percent PercentMethyl- Ethyl Catalyst Test poly-Sil- Silicate Catalyst (ExpressedRelease Tack No oxane 40 as the No. 1 Metal) 4 None... Dibutyl tindilaurate..- 0.16 0 Poor. 6 Nonedo 0. 2 0 Poor-fair. 5 None do 1.1 0Poor. 5 None. Dlbutyl tin diacetatc 0. 2 0 Poor-fair. 10 None do 0. 4 0Fair. 10 Nonedo 0.4 0 'Poor. 5 0.15 Dibutyl tin dilaurate-.. 0. 2 0 Good5 0. 15 Dlbutyl tin dlacetate---- 0. 2 0 Fair. 10 0. 15 Dibutyl tind1laurate 0. 4 0 Good. 10 l. 0 Dibutyl tin diaeetate 4. 4 0 D0. 10 1. 0Dibutyl tin dilaurate 4. 4 0 Do.

EXAMPLE 3 This example illustrates that the concentration of polyethylsilicate can be varied widely without adversely affecting the bath lifeof the treating solution or the properties of the treated paper. Thetreating solutions were prepared similarly as in Example 1. Table HIwhich" follows shows the ingredients and proportions used as well as thetest results on'the paper treated with these solutions. It will be notedthat Table III shows that within the range of from 0.15 percent to 9.0percentof as xylene, trichloroethylene, perchloroethylene, and mineralspirits present in the same proportions as the toluene used in Example 1were employed as solvents for a mixture of methylpolysiloxane No. 1,ethyl silicate 40 and dibutyl tin dilaurate as the catalyst. The methodfor making the solution was the same as that described in Example-l andthe percentages of the ingredients are found recited in the followingTable IV which also gives the results on the paper treated in suchbaths. In each instance the bath life was satisfactory for at least 6hours.

Table IV Percent Percent Percent Methyl- Ethyl Catalyst Test No. poly-Silicate (Expressed Diluent Release Tack siloxane 40 as the No. 1 Metal)10 l 4.4 Xylene 0 Good. l 0 4.4 Trichloroethylene... 0 3 Do. 10 1 0 4.4Perchloroethylene-- 0 D0. 10 1 O 4. 4 Mineral spirits 0 D0.

EXAMPLE 5 This example illustrates the preparation of toluenesolution-treating baths employing methylpolysiloxane No. 2 as thesilicone composition. The ethyl silicate 40, as well as the catalystsdescribed in this example, are the same as those employed in Example 1.The method for making the treating baths was identical with theprocedure recited in Example 1.

Table V shows the percentages of methylpolysiloxane No. 2, the ethylsilicate 40, the particular catalyst used, the percent catalyst, as wellas the bath life of the various solutions and the properties of thepaper treated with the various baths. The treatment of the paper was thesame as that described in Example No. 1.

for the above specified purposes are manifold. By means of my invention,it is possible to obtain high quality release characteristics for highlyadherent materials such as uncured synthetic rubbers, pitch, asphalt,tar, many adhesives and other type of materials. The anti-blockingproperties are effective even at low concentrations oforganopolysiloxane pickup; the paper treated can be- Table V PercentPercent Percent Test Methyl- Ethyl Catalyst No. poly- Silicate Catalyst(Expressed Bath Life Release Tack siloxane as the No. 2 Metal) 40.... 40.12 Bibutyl tin dilaurate.--. Q. 08 OK 0 Good. 41...- 4 0. l2 Dibutyltin diacetate 0. 08 Viscous after 3 hrs...-- 0 D0. 42.... 4 0. 12 Leadtetra octoate 0. 08 OK 0 Poor. 43...- 4 0.12 Lead octoate 0.08 0 Do.44..-- 4 0.12 Tin octoate 0.08 0 "Do. 4 0. l2 Tin naphthenate-- 0. 08 0Do. 46..-- 4 0.12 Tin oleate 0. 08 0 D0. 47.--. 4 0.12 Dibutyl tindioctoate. 0. 08 0 Do.

It will, of course, be apparent to those skilled 1n the for itsanti-release purposes with realization of essentially art that inaddition to the methylpolysiloxanes of viscosity recited above,'other'methylpolysiloxanes containing terminal silicon-bonded hydroxy groupsof other viscosities within the range of to 2 million centipoises, whenmeasured at 25 C. can be employed without departing from the scope ofthe invention. The concentration of the polydimethylsiloxane, as well asof the catalyst and emulsifying agent (where employed), may be variedwithin the ranges previously recited, again within the scope of thepresent invention. The concentration of the dibutyl tin dilaurate or thedibutyl tin diacetate (or mixtures of such tin salts) may also be variedwithin wide limits depending on the factors recited previously.

The amount of organopolysiloxane which is picked up by the cellulosicmaterial as a result of the treatment with the emulsion or solution ofthe organopolysiloxane depends upon such factors as the absorbency ofthe cellulosic material, the method of application, the concentration oforganopolysiloxane solution or emulsion, etc. Generally, the amount oforganopolysiloxane pickup ranges from about 0.2 to about 5%, or more,based on the dry weight of the cellulosic material; the preferred pickupbeing within the range of about 0.5 to about 2% organopolysiloxanepickup. Obviously, larger amounts of organopolysiloxane pickup may beemployed, but generally this is not necessary and usually serves merelyto increase the cost of the treatment. The ability to obtain maximumpickup with minimum amounts of organepolysiloxane and to realize themaximum release properties is one of the unexpected and unobviousadvantages of employing the particular combination of ingredients hereindescribed for release purposes.

Advantages of using the compositions herein described optimumproperties. Heretofore, organopolysilolxanes previously available on themarket for the same purpose required aging, that is, storing of thetreated paper for times as long as six weeks, in order to bring out theoptimum release characteristics of the treated paper. Of considerableimportance is the fact that eve-n at high temperatures, the releasecharacteristics are maintained at optimum levels and elevatedtemperatures do not destroy the release film. The compositions fortreating cellulosic materials herein described are readily amenable to asingle step procedure and are easily regulated and controlled foradjustable organopolysiloxane pickup by minor variations informulations. Standard paper making or paper converting equipment isreadily employed in connection with the treating operations and noprecautions need be taken for any toxic materials which may be containedin the treating emulsions.

Cellulosic materials treated as described above have a wide range ofusefulness. Thus, asphalt or high molecular weight organic polymers,such as various synthetic rubbers, can be poured hot into containersfashioned from the treated paper or paperboard, and after cooling itwill be found that solidified asphalt or polymer is readily and cleanlyseparated from container Walls.

My invention permits paper treated in accordance 'With my process to besubstituted for various fabrics which have heretofore been used incontact with adhesive surfaces of electricians pressure-sensitive tape,adhesive tapes used for surgical purposes, and regenerated cellulosetapes carrying a permanent adhesive upon one surface. Vulcanized orunvulcanized sheets of rubber can be prevented from adhering to eachother despite the fact that these sheets of rubber are quite sticky andcohesive when in direct contact with each other. Paper treated inaccordance with the instant invention is also useful in lining variousboxes of partially prebaked goods such as buns, rolls and the like, andadvantage can be taken of the outstanding release properties at elevatedtemperatures by completing the baking cycle in the origi-' (1) from 1 to20 parts of a linear polydimethyl-siloxane containing a terminalsilicon-bonded hydroxy group,

(2) from 0.1 to 40 parts of a polyalkyl silicate,

(3) from 0.01 to parts of a metallic salt selected from the classconsisting of dibutyl t-in dilaurate and dibutyl tin diacetate, and

(4) from 75 to 97 parts of an organic solvent, and thereafter drying thetreated material.

2. The method for rendering cellulosic fibrous sheet materialnon-adherent to surfaces which normally adhere thereto, which processcomprises treating the cellulosic fibrous sheet material with a treatingbath containing, by weight, the following sole active ingredients:

(1) from 1 to 20 parts of a linear polydimethyl-siloxane containingterminal silicon-bonded hydroxy groups,

(2) from 0.1 to 40 parts of a polyethyl silicate,

(3) from 0.01 to 5 parts dibutyl tin dilaurate, and

(4) from 75 to 97 parts of an organic solvent, and thereafter drying thetreated material.

3. The method for rendering cellulosic fibrous 'sheet'" materialnon-adherent to surfaces which normally adhere thereto, which processcomprises treating the cellulosic fibrous sheet material with a treatingbath containing, by weight, the following sole active ingredients:

(1) from 1 to 20 parts of a linear polyclimethyl-siloxane containingterminal silicon-bonded hydroxy groups,

(2) from 0.1 to 40 parts of a polyalkyl silicate,

-( 3) from 0.01 to 5 parts dibutyl tin diacetate, and

(4) from to 97 parts of an organic solvent, and thereafter drying thetreated material.

4. The method for rendering cellulosic fibrous sheet materialnon-adherent to surfaces which normally adhere thereto, Which processcomprises coating the said fibrous sheet material with an aqueousemulsion containing as the sole' active ingredient, by weight, (1) from1 to 20 parts of a linear polydimethyl-siloxane containing terminalsilicon-bonded hydroxy groups, (2) from 0.1 to 40 parts of polyalkylsilicate, and (3) from 0.01 to 5 parts of a metallic salt selected fromthe class consisting of dibutyl rtin dilaurate and dibutyl tindiacetate, and thereafter drying the coated material.

5. The method for rendering cellulosic fibrous sheet materialnon-adherent to surfaces which normally adhere thereto, which processcomprises coating the said fibrous sheet material with an organicsolution consisting essentially of, by weight, the following essentialingredients: (1) from 1 to 20 parts of a linear polydimethylsiloxanecontaining terminal silicon-bonded hydroxy groups, (2) from 0.1to' 40parts of polyethyl silicate and (3) from 0.01 to 5 parts of dibutyl tindilaurate, and thereafter drying the coated material.

6. The method for rendering cellulosic fibrous sheet materialnon-adherent to surfaceswhich normally adhere thereto, which processcomprises coating the said fibrous sheet material with an organicsolution consisting essentially of, by weight, the following essentialingredients: (1) from 1 to 20 parts of a linear polydimethylsiloxanecontaining terminal silicon-bonded hydroxy groups, (2) from 0.1 to 40parts of polyethyl silicate and (3) from 0.01 to 5 parts of dibutyl tindiacetate, and thereafter drying the coated material.

7. Cellulosic sheet material treated in accordance with the methoddescribed in claim 1.

References Cited in the file of this patent UNITED STATES PATENTS,2,504,388-- Braley Apr. 18, 1950 2,588,367 Dennett Mar. 11, 19522,814,601 Currie et a1. Nov. 26, 1957 2,843,555. Berridge July 15, 1958

1. THE METHOD FOR RENDERING CELLULOSIC FIBROUS SHEET MATERIALNON-ADHERENT TO SURFACES WHICH NORMALLY ADHERE THERETO, WHICH PROCESSCOMPRISES TREATING THE CELLULOSIC FIBROUS SHEET MATERIAL WITH A TREATINGBATH CONSISTING ESSENTIALLY OF, BY WEIGHT, THE FOLLOWING ACTIVEINGREDIENTS: (1) FROM 1 TO 20 PARTS OF A LINEAR POLYDIMETHYL-SILOXANECONTAINING A TERMINAL SILICON-BONDED HYDROXY GROUP, (2) FROM 0.1 TO 40PARTS OF A POLYALKYL SILICATE, (3) FROM 0.01 TO 5 PARTS OF A METALLICSALT SELECTED FROM THE CLASS CONSISTING OF DIBUTYL TIN DILAURATE ANDDIBUTYL TIN DIACETATE, AND (4) FROM 75 TO 97 PARTS OF AN ORGANICSOLVENT, AND THERE AFTER DRYING THE TREATED MATERIAL.